Hemodynamic and functional data will be measured in isolated dog kidneys perfused with blood and artificial media to provide a critical perspective for physiologic data generated by these techniques. Mechanisms of tachyphylaxis to angiotensin II and its reversal will be studied and the results applied to kidneys in vivo for determination of relationships to acute renal failure and malignant hypertension. The synthesis, metabolism and excretion of catecholamines will be evaluated in the isolated preparation. Similarly a model of acute renal failure will be developed in the isolated kidney by altering the oncotic and viscous properties of the perfusate.